Small Craft Advisory 357, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
146 PM AKDT TUE APR 29 2014

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL PATTERN TODAY CONSISTS OF HIGH AMPLITUDE TROUGHS
AND RIDGES. THERE IS A RIDGE EXTENDING UP THE WEST COAST OF NORTH
AMERICA INTO THE SOUTHERN PANHANDLE OF THE STATE WITH ANOTHER HIGH
AMPLITUDE RIDGE BUILDING INTO THE EASTERN BERING SEA AND INTO
SOUTHWEST ALASKA. SANDWICHED IN BETWEEN THESE RIDGES IN A TROUGH
THAT EXTENDS FROM THE ALCAN BORDER THROUGH THE GULF AND THEN
FARTHER SOUTHWARD TO 30N. THE WESTERN ALEUTIANS ARE BEING
IMPACTED BY ANOTHER HIGH AMPLITUDE TROUGH THAT IS OVER THE
KAMCHATKA PENINSULA AND WESTERN BERING SEA.
AT THE SURFACE THERE IS A MODERATE LOW IN THE WESTERN BERING SEA
AND A FRONT AHEAD OF IT IN THE CENTRAL BERING SEA. THESE FEATURES
WILL SLOW THERE EASTERLY PROGRESS AS THEY ARE STOPPED BY THE RIDGE
OF HIGH PRESSURE OVER SOUTHWEST AND SOUTHCENTRAL ALASKA.
THIS RIDGE IS ALSO STOPPING THE PROGRESS OF A LOW IN THE NORTHEAST
GULF OF ALASKA...WHICH IS RAPIDLY WEAKENING AND SHOULD DISSIPATE
BY TOMORROW.

&&

.MODEL DISCUSSION...
WITH THE RIDGE BUILDING INTO THE STATE BECOMING THE MAIN WEATHER
FEATURE THE MODELS ARE IN GOOD AGREEMENT WITH THIS RELATIVELY
STABLE PATTERN. THEY ALL KEEP THE STORM TRACK AWAY FROM MAINLAND
ALASKA THROUGH EARLY NEXT WEEK AT LEAST. THERE IS SOME
SIGNIFICANT DIVERGENCE IN SOLUTIONS BY THE MIDDLE OF NEXT
WEEK...BUT THIS IS NOT UNUSUAL AND THE DIFFERENCES WILL LIKELY
WORK OUT WITH SUCCESSIVE MODEL RUNS.

&&

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...THE ATMOSPHERE IS MORE STABLE THIS AFTERNOON
THAN YESTERDAY AFTERNOON WHICH SHOULD MINIMIZE THE CHANCE OF
AFTERNOON AND EVENING SHOWERS AROUND SOUTHCENTRAL.
THE LOW IN THE NORTHEAST GULF IS RAPIDLY WEAKENING AS IT PUSHES
INTO THE RIDGE OVER SOUTHCENTRAL ALASKA. THIS LOW WILL PUSH A FEW
CLOUDS TO THE NORTHERN GULF COAST BUT THEY WILL LIKELY BE GONE BY
MORNING. THIS PRESSURE DIFFERENCE BETWEEN THE HIGH AND LOW WAS THE
CAUSE OF THE GUSTY WINDS IN WHITTIER AND SEWARD TODAY. HOWEVER
THESE SHOULD ALSO SUBSIDE BY LATE THIS EVENING AS THE LOW
DISSIPATES. A WEAKENING FRONT THAT MOVED ACROSS SOUTHWEST AND
WESTERN ALASKA LAST NIGHT IS SPILLING A FEW CLOUDS OVER THE ALASKA
RANGE INTO THE SUSITNA VALLEY THIS AFTERNOON. HOWEVER THE RIDGE
WILL LIKELY KEEP CLOUD COVER FROM THIS FRONT SHORT LIVED WITH
CLEAR SKIES BEING THE OVERALL RULE AGAIN BY MORNING.

SOUTHWEST ALASKA...
THE FRONT THAT MOVED THROUGH THE KUSKOKWIM DELTA LAST NIGHT INTO
THIS MORNING CONTINUES TO WEAKEN AS IT MOVES EASTWARD. THERE IS
MORE ENERGY WITH IT FARTHER NORTH SO THERE IS A BETTER CHANCE FOR
SOME RAIN WITH IT IN THE KUSKOKWIM VALLEY THIS EVENING THAT
FARTHER SOUTH. THE BRISTOL BAY REGION MAY SEE A FEW SHOWERS ALONG
THE ALEUTIAN RANGE WITH A LITTLE EXTRA LIFT FRONT THIS FRONT BUT
THEY SHOULD NOT BE WIDESPREAD. LOW CLOUDS AND AREAS OF FOG ALONG
THE COAST WILL PUSH FARTHER INLAND AGAIN TONIGHT AS THE LARGE
RIDGE CREATES STRONG SUBSIDENCE UNDER IT WHICH IS FAVORABLE FOR
THE FOG AND STRATUS.

BERING SEA/ALEUTIANS...
THE LOW THAT IS NEAR SHEMYA THIS AFTERNOON WILL CONTINUE TO TRACK
TO THE NORTH. THERE WILL BE SOME RAIN SHOWERS AND FOG FROM ATKA
WESTWARD WITH THIS LOW. THE FRONT ASSOCIATED WITH THIS LOW THAT
IS MOVING EASTWARD IS WHAT WILL BRING IN THE GALE FORCE WINDS AND
RAIN TO THE CENTRAL ALEUTIANS THROUGH PARTS OF THE ALASKA
PENINSULA OVER THE NEXT DAY OR TWO. THIS FRONT WILL HAVE TROUBLE
PROGRESSING EASTWARD BY TOMORROW AS THE RIDGE IN SOUTHWEST ALASKA
STRENGTHENS.
&&

.LONG TERM FORECAST...
THE BIG STORY IN THE LONG TERM WILL BE THE LARGE RIDGE BUILDING
INTO THE REGION FOR THE SECOND HALF OF THIS WEEK AND INTO EARLY
NEXT WEEK. THIS RIDGE WILL NOT ONLY BRING THE DAYTIME HIGHS 10
DEGREES OR MORE ABOVE NORMAL...BUT ALSO USHER IN THE DRIEST
CONDITIONS OF THE SEASON SO FAR. THE BIGGEST UNCERTAINTY AS TO HOW
WARM IT WILL GET IS WHETHER A WEAK LOW WILL BE ABLE TO DEVELOP IN
THE NORTHERN GULF OF ALASKA. IF A WEAK LOW DOES DEVELOP IT WILL
INCREASE THE OFFSHORE WINDS AND INCREASE TEMPERATURES BOTH ALONG
THE COAST AND INLAND. THIS PERIOD OF QUIET WEATHER WILL LIKELY
THEN CONTINUE INTO AT LEAST EARLY NEXT WEEK AS NO MAJOR SYNOPTIC
SCALE SYSTEMS ARE IN THE FORECAST FOR THE NEXT WEEK. &&

.FIRE WEATHER...
THE HIGH PRESSURE BUILDING IN THIS WEEK WILL USHER IN WARMER
TEMPERATURES AND DRIER AIR THURSDAY...FRIDAY...AND INTO THE
WEEKEND. WINDS WILL GENERALLY BE ON THE LIGHTER SIDE THROUGH
THURSDAY...BUT A LOW IN THE GULF OF ALASKA MAY INCREASE OFFSHORE
WINDS ON FRIDAY. RELATIVE HUMIDITY VALUES WILL DROP INTO THE LOW
20S TO POSSIBLY TEENS ACROSS PORTIONS OF SOUTHERN ALASKA.
&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 170 172 173 174 175 176 177 179 185.
FIRE WEATHER...NONE.
&&

APR 14